Chair back



FIG. 1 is a front perspective view of the chair back in accordance with the present invention;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top view thereof;

FIG. 7 is a bottom view thereof; and,

FIG. 8 is another perspective view thereof showing a chair in broken line.

The portions of the design shown in broken line are present for illustrative purposes only and form no part of the claimed design. 

The ornamental design for chair back, as shown and described. 